A high-luminance discharge lamp has been the mainstream before as a light source unit used in projectors, etc. for a presentation or a digital cinema. However, in recent years, the number of products has been increased that adopt solid-state light-emitting devices such as light emitting diodes (LEDs) and laser diodes (LDs).
The light source unit adopting the solid-state light-emitting devices includes a configuration in which particulate phosphors are irradiated with light (excitation light) from, for example, the LEDs or the LDs, and thereby white color light as fluorescence is extracted. The particles of phosphor (phosphor particles) are generally fixed on a substrate as a phosphor layer that is mixed with a binder. In such a light source unit, the phosphor particles are dispersed in the binder, and thus, it is difficult to shorten the distance between the particles. Therefore, it is not possible to increase the filling rate of the particles per unit volume, and thus, it is difficult to improve the conversion efficiency to fluorescence. Further, such a phosphor layer has a large amount of light propagation in a surface direction. This causes the area of emitting light with respect to the area of being irradiated with the excitation light to become large, which leads to the reduction in light use efficiency. Furthermore, the fluorescence that has been converted by the phosphor particles is outputted to the outside via the binder. This causes the fluorescence to be absorbed within the binder, leading to the deterioration of light intensity.
To address this, for example, PTL 1 discloses a light-emitting device including a phosphor layer that allows a portion of the phosphor particles to be exposed from the binder. In such a light-emitting device, allowing the portion of the phosphor particles to be exposed from the binder leads to the reduction in light loss caused due to the propagation of the fluorescence in the binder.